Dear Thang,
32 time bins are added at the beginning of the internal, high temporal
resolution stimulus functions used to create regressors for the design
matrix after convolution, see spm_get_ons.m and spm_fMRI_design.m.
They correspond to 2 TRs at the default microtime resolution of 16.
They allow to model trials taking place just before or at the beginning
of the acquisition (using negative onsets).
In the context of DCM, I would recommend you to use spm_dcm_U.m so that
you don't have to deal with these implementation details.
Best regards,
Guillaume.
On 18/10/16 15:32, Thang Le wrote:
> Dear DCM experts,
>
> Could anyone please let me know the reason behind excluding the first 32
> values of SPM.Sess.U.u when inputing this data into DCM (e.g.,
> DCM.U.u=[SPM.Sess.U(i).u(33:end,1)...])?
>
> Thank you in advance for your explanation.
>
> Thang
--
Guillaume Flandin, PhD
Wellcome Trust Centre for Neuroimaging
University College London
12 Queen Square
London WC1N 3BG
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